If it's a square taper BB then it's not an expensive upgrade and probably worth doing. What size of biopace chainrings do you need? I know the co-op in my town has a bunch of different ones and I am sure other co-ops might too. If the chainrings have sharp tips on the teeth then they're toast unfortunately. A new 7 speed freewheel shouldn't be too expensive but you can still get high quality ones from IRD, they make a few different gear range. The shimano ones work well enough though.